In a previous patent application by Willie T. Grant for a self-operating air register damper, a device is disclosed for automatically controlling the movement of a damper plate pivotally mounted within an associated damper housing, said housing being inserted into the terminal opening of furnace duct boot when said boot terminates in room air register. Specifically, the self-operating damper plate is rotated by the drive belt connecting motor shaft pulley to damper plate pulley, or rotation of said damper plate is accomplished by optional gear drive means.
In practice, the damper housing, constructed to dimensions compatible with standard size duct boots, is not always accepted by said duct boots due to dimensional changes made in the field to aforesaid boots, said dimensional modifications being required to solve ducting installation problems. Additional alterations to make duct boots accept damper housings can be time consuming and costly when said housings encounter altered geometrical shapes of duct boots which are incompatible with standard dimensions and inherent rigidity of said damper housings.